Researchers using an underwater robot off Florida seek more clues about deep-sea reefs  a vast mystery of the depths.

By Ludmilla LelisJanuary 20, 2011Reporting from Orlando, Fla.

In the Atlantic Ocean off Florida's coast, at 1,500 feet and deeper, the water is 45 degrees and pitch-black. Yet life thrives there.

Scientists are just beginning to explore this vast secret of the deep: extensive coral reefs and the marine creatures that live there because of them.

A mission in November explored more than 800 square miles of ocean, from Jacksonville to the Keys, confirming the existence of several deep-water reefs and charting new sites.Like the corals found in shallow, tropical reefs, deep-sea corals help form habitat for crabs, shrimp, fish and other marine life. Growing from the seafloor, the corals have produced massive cliffs through the centuries as new generations of coral grow atop the old.Scientists already know that deep-water corals attract commercially important fish, offering protection for the young and places to reproduce for sea bass, snapper, porgy and rock shrimp.

Unlike the easily accessible tropical coral reefs, however, these deeper corals have many unknowns. Scientists suspect massive mounds of the corals are still undiscovered and that the habitats are vital to the overall health of marine life. Exactly what role the reefs play for the survival of fish populations and the benefit of people is unknown.

There are a few tantalizing possibilities. Early studies indicate that some species found only on deep-sea coral reefs have possible medical uses. A unique sponge, for example, is being used in cancer treatment studies.

But first, researchers are still trying to answer basic questions: What is down there? What lives there?

"With every expedition, every time we dive, we find more and more coral," said Steve Ross, a University of North Carolina-Wilmington professor and the expedition's chief scientist. "These coral reefs are extremely diverse and abundant and widely distributed."

Research about the deep reefs off the Southeastern U.S. started in earnest only a decade ago, but they are already federally protected. Officials declared more than 23,000 square miles of ocean off-limits to bottom trawling, a fishing practice that has destroyed similar reef systems off the European coast. Only one commercial fishing group, a small outfit that catches golden crab, continues to trap the crustacean among the deep-sea corals, and it works with federal managers to limit the effect on the reefs.

For scientists, just reaching the reefs is difficult because the corals thrive in depths of 1,300 feet to 3,200 feet, well beyond diving range for humans.

This year's expeditions depended on the Jason 2, a 9,000-pound, remotely operated vehicle from the Massachusetts-based Woods Hole Oceanographic Institution. Equipped with several cameras and robotic arms to collect samples, it was dispatched to the ocean floor for days at a time, exploring seven key reefs.

Carrying the vehicle, 56 researchers and crew for the 15-day expedition was the Ronald H. Brown, the National Oceanic and Atmospheric Administration's largest vessel. NOAA's coral reef conservation program sponsored the trip, which included researchers from seven academic and scientific organizations.

Ross and Andrew David, a research fishery biologist with NOAA Fisheries, said the Jason 2 proved invaluable. "Sonar had suggested there was more coral, and we were able to confirm that," David said. "There are several ongoing studies trying to age the corals using radioactive carbon dating, which suggests some of these reefs are 2,000 years old."

Last year's research will help federal managers refine the protected area and include some of the new reefs that were discovered, Ross said.

But with many hours of video and other data collected, and with rare samples taken from the reefs, Ross said some of the greatest insights were yet to come.

"It may be years before the data can be analyzed and some of the big picture comes out," Ross said. "But it's so difficult to study these reefs that every cruise we can take, we learn a lot."